For RPi using the U2D2 is best. Combine it with the DXL SDK. You will need these XL-320 convertible cables
And these hubs
You can look at this free Kindle sample for some ideas
https://www.amazon.com/Projects-Guide-ROBOTIS-ENGINEER-2-ebook/dp/B09GN3VJ9P
Or at this post for a more conceptual approach at what needs to be done